1. Field of Invention
The present invention relates to an aerosol composition. More particularly, the invention relates to an aerosol composition having a water-alcohol base which composition is much improved in the emulsion stability.
2. Description of Prior Art
Aerosol products have heretofore been used as glass cleaners, furniture cleaners, other various cleaners, deodorants, insecticides, cosmetics and the like. In these aerosol products, in order to attain a good compatibility with a propellant, solvents such as lower alcohols are used as the base, and effective or pharmaceutically effective components are dissolved or dispersed in these solvents. However, these solvent bases having aerosols are dangerously inflammable, and an expensive, incombustible gas such as Freon (fluorohydrocarbons, the Trade Mark of E. I. Dupont De Nemours & Co.) should be used as the propellant. Further, a component insoluble in a solvent such as ethanol is often used as an effective component. Accordingly, aerosol products in which a water or water-alcohol base is used and a cheap lower hydrocarbon is used as a propellant now attract attention in the art as economical and safe aerosol products.
However, since water and such propellant are incompatible with each other and they differ from each other with respect to the specific gravity, it is very difficult to prepare a homogeneous aerosol from them. More specifically, in an aerosol product comprising a starting liquid of a water base and a propellant, it is very difficult to mix the starting liquid with the propellant uniformly, and the composition gets readily separated into two layers, namely the layer of the starting liquid and the layer of the propellant. As means for overcoming this defect, there has been proposed a method in which several surface active agents are used as an emulsifier to improve the emulsion state between the starting liquid and the propellant. However, satisfactory results could not always be obtained even according to that method because anionic surfactants have corrosive action to a metallic container for the aerosol and nonionic surfactants were also unsatisfactory.
Further, some of the effective or pharmaceutically effective components are water-insoluble. In order to disperse those water-insoluble components stably, a starting liquid having a water-alcohol base containing 30 to 80 wt.% of alcohol, which is formed by adding, for example, a lower alcohol such as methanol, ethanol, and isopropanol to water is preferable, compared with a starting liquid having a water base. In addition, the amount of the emulsifier is preferred to be as small as possible, especially not more than 1 wt.%, in order that the composition may contain a sufficiently large amount of effective components.
However, in an aerosol composition having a water-alcohol base, breaking of the emulsion state between the propellant and the base liquid is more readily caused than in an aerosol composition having the water base alone. Especially in the case of an aerosol composition having a water-alcohol base containing 30 to 80%, especially 40 to 70%, by weight of the alcohol, none of the conventional surface active agents are capable of providing an excellent emulsion state between the base and propellant.